Beam forming and pointing in a network of unmanned aerial vehicles (uavs) for broadband access

ABSTRACT

Systems and methods configured to form and point beams from one or more unmanned aerial vehicles (UAVs) toward a target coverage area on the ground. One embodiment describes dividing the target coverage area on the ground among multiple UAVs when each UAV antenna system generates static beams. Another embodiment describes dividing the target coverage area on the ground among multiple UAVs when their antenna systems are capable of dynamically steering their respective beams. Another set of embodiments describe systems and method to allow multiple UAVs to provide service in the same area on the ground using the same spectrum.

PRIORITY AND RELATED APPLICATIONS

This application is a divisional of and claims priority to co-owned U.S.patent application Ser. No. 14/626,698, filed Feb. 19, 2015 and entitled“BEAM FORMING AND POINTING IN A NETWORK OF UNMANNED AERIAL VEHICLES(UAVS) FOR BROADBAND ACCESS”, that claims priority to co-owned U.S.Provisional Patent Application Ser. No. 62/076,360 filed Nov. 6, 2014,and entitled “BEAM FORMING AND POINTING IN A NETWORK OF UNMANNED AERIALVEHICLES (UAVS) FOR BROADBAND ACCESS”, and co-owned U.S. ProvisionalPatent Application Ser. No. 62/080,856 filed Nov. 17, 2014, and entitled“BEAM FORMING AND POINTING IN A NETWORK OF UNMANNED AERIAL VEHICLES(UAVS) FOR BROADBAND ACCESS”, each of which is incorporated herein byreference in its entirety.

The application is related to co-owned, co-pending U.S. patentapplication Ser. No. 14/516,491 entitled “UNMANNED AERIAL VEHICLE (UAV)BEAM FORMING AND POINTING TOWARD GROUND COVERAGE AREA CELLS FORBROADBAND ACCESS”, filed on Oct. 16, 2014, co-owned, co-pending, U.S.patent application Ser. No. 14/486,916, entitled “ANTENNA MANAGEMENT ANDGATEWAY DESIGN FOR BROADBAND ACCESS USING UNMANNED AERIAL VEHICLE (UAV)PLATFORMS”, filed Sep. 15, 2014, co-owned, co-pending, U.S. patentapplication Ser. No. 14/295,160, and entitled “METHODS AND APPARATUS FORMITIGATING FADING IN A BROADBAND ACCESS SYSTEM USING DRONE/UAVPLATFORMS”, filed on Jun. 3, 2014, and co-owned, U.S. patent applicationSer. No. 14/222,497, and entitled “BROADBAND ACCESS TO MOBILE PLATFORMSUSING DRONE/UAV”, filed on Mar. 21, 2014, each of the foregoingincorporated by reference herein in its entirety.

COPYRIGHT

A portion of the disclosure of this patent document contains materialthat is subject to copyright protection. The copyright owner has noobjection to the facsimile reproduction by anyone of the patent documentor the patent disclosure, as it appears in the Patent and TrademarkOffice patent files or records, but otherwise reserves all copyrightrights whatsoever.

BACKGROUND

1. Technological Field

The present disclosure describes aspects of a system for broadbandInternet access using unmanned aerial vehicles (UAVs) as a platform torelay Internet traffic among different types of terminals. Thedisclosure describes systems and methods for optimally pointing thebeams of the UAV toward the coverage area on the ground, and adjustingthe beams toward the ground coverage area based on the UAV's altitude,UAV movements, and UAV motions such as roll/pitch.

2. Description of Related Technology

As Internet traffic has increased over the years, new technologies areneeded to deliver broadband access to homes and enterprises at lowercost and to places that are not yet covered. Examples of currentbroadband delivery systems include terrestrial wired networks such asDSL (Digital Subscriber Line) on twisted pair, fiber delivery systemssuch as FiOS (Fiber Optic Service), and geo-stationary satellitesystems. The current broadband access systems have a number ofshortcomings. One issue is lack of service in remote and lightlypopulated areas. Geo-stationary satellites do provide service in remoteareas of many developed countries. Areas of the world with relativelyunderdeveloped network infrastructures, however, lack adequate satellitecapacity.

A notable reason satellite capacity has not been adequately provided incertain regions of the world is the relatively high cost of satellitesystems. Due to adverse atmospheric effects in satellite orbits,satellite hardware must be space qualified and is costly. Launchvehicles to put the satellites in orbit are also costly. Moreover, dueto the launch risk and high cost of satellites, there is a significantcost to insure the satellite and the launch. Therefore, broadbandsatellite systems and services are relatively costly and difficult tojustify in those regions. It is also costly to deploy terrestrialsystems such as fiber or microwave links in lightly populated regions.The small density of subscribers does not justify the deployment cost.

SUMMARY

The present disclosure describes, inter al/a, systems and methods forrelaying Internet traffic via a network of unmanned aerial vehicles(UAV).

A method of relaying Internet traffic via an unmanned aerial vehicle(UAV) is disclosed. In one embodiment, the method includes: associatingeach of a plurality of ground terminals to respective ones of aplurality of cells; receiving data at the UAV from a gateway apparatus,the gateway apparatus being in data communication with an Internet; andtransmitting a beam including at least a portion of the received data tothe plurality of cells, the associated ones of the plurality of groundterminals being in data communication with the UAV; where adjacent onesof the plurality of cells receive the beam at different frequencies.

In a first variant, the UAV and at least one ground terminal of theplurality of ground terminals include antenna sub-systems having twoantenna polarizations. In one sub-variant, the two antenna polarizationsinclude vertical and horizontal linear polarizations. In anothersub-variant, the two antenna polarizations include left and rightcircular polarizations. In still a third sub-variant, the UAV and the atleast one ground terminal include two transmitter and two receiverchains, and each of the transmitter and receiver chains are connected toone of the two antenna polarizations. In one such exemplaryimplementation, the UAV and the at least one ground terminal areconfigured to transmit and receive two data streams, on each one of thetwo antenna polarizations.

In a second variant, the UAV forms a plurality of beams to cover atarget coverage area on the ground. In one such case, at least a firstone and a second one of the plurality of beams use differenttransceivers.

In a third variant, the UAV and the ground terminal communicateaccording to an IEEE 802.11 physical air interface protocol. In onesub-variant, the UAV and the ground terminal are configured to executean IEEE 802.11 medium access control (MAC) layer that is configured tosynchronize to a timing signal generated from a Global PositioningSystem (GPS) receiver. In a second-sub-variant, the UAV and the at leastone ground terminal are configured to execute an IEEE 802.11 mediumaccess control (MAC) layer that is configured to synchronize to a masterUAV transceiver. In some implementations, the master UAV transceiverprovides a clock timing reference to at least one other transceiverwithin the UAV. In other implementations, the master UAV transceiverprovides a clock timing reference via a beacon message to the UAV.

A system for relaying Internet traffic via an unmanned aerial vehicle(UAV) is disclosed. In one embodiment, the system includes: a network ofone or more unmanned aerial vehicles (UAV) that are configured toassociate to respective ones of a plurality of ground terminals within aplurality of cells; wherein each of the one or more UAVs are configuredto receive from a gateway apparatus, and where the gateway apparatus isin data communication with an Internet; and where each one of the one ormore UAVs transmit at least a portion of the received data to therespective ones of the plurality of ground terminals within theplurality of cells.

In one variant, the network of one or more UAV are synchronized to acommon clock reference. In one sub-variant, the common clock referenceis derived from a beacon message transmitted by a master UAV. In asecond sub-variant, each one of the one or more UAVs are allocated atleast one uplink sub-interval and at least one downlink sub-intervalthat are generated from the common clock reference. In a thirdsub-variant, each one of the one or more UAVs allocate a plurality oftime slots associated with the at least one uplink sub-interval and atleast one downlink sub-interval to the respective ones of the pluralityof ground terminals.

A system for relaying Internet traffic via an unmanned aerial vehicle(UAV) is disclosed. In one exemplary embodiment, the system includes: agateway apparatus in data communication with an Internet; a network ofone or more unmanned aerial vehicles (UAV) that are configured tocommunicate to respective ones of a plurality of ground terminals withina plurality of cells in data communication with the gateway apparatus;wherein the network of one or more UAVs are associated with a pluralityof cells, and where adjacent ones of the plurality of cells areallocated different frequencies for communication.

In one variant, the network of one or more UAV are synchronized to acommon clock reference. In one sub-variant, the network of one or moreUAV are configured to transmit or receive during a common time intervalbased on the common clock reference.

These and other aspects shall become apparent when considered in lightof the disclosure provided herein.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following figures, similar components are identified using thesame reference label. Multiple instances of the same component in afigure are distinguished by inserting a dash after the reference labeland adding a second reference label.

FIG. 1A is a graphical depiction of an aerial platform basedcommunications system of some embodiments.

FIG. 1B is a graphical depiction of the radio sub-system of the aerialplatform of some embodiments.

FIG. 1C is a graphical depiction of the radio sub-system of the groundterminal of the aerial platform based communications system of someembodiments.

FIG. 2A is a graphical depiction of a set of beams formed by two aerialplatforms/UAVs on the ground.

FIG. 2B is a graphical depiction of a set of beams formed according toan embodiment by three aerial platforms/UAVs on the ground.

FIG. 2C is a graphical depiction of a set of beams formed according toan embodiment by two aerial platforms/UAVs on the ground.

FIG. 3A is a graphical depiction of two UAVs providing coverage to thesame area on the same frequency.

FIG. 3B is a graphical depiction of two UAVs providing coverage to thesame area on the same frequency.

DETAILED DESCRIPTION

This disclosure describes aspects of a system designed to providebroadband access. The aerial platforms to which the embodiments of thisdisclosure apply may be drones, unmanned aerial vehicles (UAVs),balloons, blimps, airships, etc. The drone or UAV may comprisepropulsion systems, fuel systems, and onboard navigational and controlsystems. In one exemplary embodiment the drone comprises a fixed wingfuselage in combination with a propeller, etc. In other embodiments, theUAV comprises a robocopter, propelled by a rotor. The UAV may carry fuelonboard or function using electrical (e.g., battery powered) and/orsolar energy. In the remainder of this disclosure, the terms “aerialplatform” and “UAV” refer to any of the above mentioned platforms suchas drones, balloons, blimps, airships, etc. Conversely, reference toUAVs, drones, balloons, blimps, airships, etc. in the disclosure canrefer to aerial platforms in general or any other type of aerialplatforms.

FIG. 1A shows one UAV 110. Each UAV 110 has a drone radio sub-system112, a message switch sub-system 116, and at least one drone antennaaperture sub-system 114 that is configured to generate a “beam” or“footprint” of radio coverage.

The exemplary block diagram of the radio sub-system 112 shown in FIG. 1Bconsists of five sub-systems: (1) a receiver 318 that demodulates anddecodes the signal received from antenna sub-system 114; (2) atransmitter sub-system 316 that modulates the data received from aprocessor 314 and sends the resulting signal to a power amplifier (PA)sub-system 317 and then an antenna sub-system 114; (3) the processorsub-system 314, which carries out functions such as configuring thereceiver 318 and transmitter 316 sub-systems, processing the datareceived from the receiver 318 sub-system, determining the data to betransmitted through the transmitter sub-system 316, as well ascontrolling the antenna sub-system 114; (4) a memory sub-system 312 thatcontains program code, configuration data, and system parameterinformation that are accessed by the processor 314 for execution; and(5) a gyroscope/accelerometer/GPS (Global Positioning System) sub-system319 to determine the position coordinates and orientation angles such asroll/pitch angles of the UAV 110.

Depending on the altitude of the UAV 110, each UAV 110 covers an area onthe ground. Typically, the coverage area may have a radius of as low asa few tens of kilometers and as much as 200 km or more, although thoseof ordinary skill in the related arts will readily appreciate thatsmaller and/or greater coverage areas are possible. UAVs 110 communicatewith at least two kinds of ground terminals: one type is a user GroundTerminal (GT) 120 (see FIG. 1A), which may include terminals at a homeor enterprise that are configured to provide Internet connectivity tothe home or enterprise; a second type is an Internet Gateway Terminal(GWT) 130, which communicates with UAV 110 on paths 212 and 232 using agateway radio sub-system module 132 and an antenna sub-system 134. Whilethe disclosed embodiments are discussed primarily with reference tofixed terminals or devices on the ground, those of ordinary skill in therelated arts will readily appreciate that the principles describedherein equally apply to terminals or devices attached to mobileplatforms such as boats, ships, airplanes, trucks, and/or other mobileplatforms/vehicles.

GTs 120 transmits and receives data on paths 222 and 212, respectively,from the Internet 136 using the UAV 110 as an intermediary to the GWT130. The GWT 130 radio sub-system module 132 may communicate with theInternet 136 by connecting via a local area network (LAN), local areawireless (e.g., Wi-Fi), Bluetooth, cellular, radio, infrared, or anyother type of data connection. User devices such as personal computersand mobile devices can connect to the UAV 110 through a number of proxydevice(s) in the network between the GT 120 and the user device. In someembodiments, the UAV's 110 radio sub-system aggregates traffic receivedfrom at least one GT (up to all GTs) 120 and sends the aggregated datato the Internet 136 via one of the GWTs. In order to support aggregateddata streams, the GWTs 130 may need to provide higher data rates fromand to the UAVs 100 than the GTs 120, accordingly the gain of the GWTantenna sub-system 134 may be larger than that of the GT 124, and theGWT transmitter may transmit at higher power than the GT's 416 do.

As shown in FIG. 1A, the GT 120 has two main sub-systems, a groundterminal radio sub-system 122, and a ground terminal antenna sub-system124. As shown in FIG. 1C, the GT radio sub-system 122 consists of 4sub-systems: (1) a receiver 418 that demodulates and decodes the signalfrom drone antenna sub-system 114; (2) a transmitter sub-system 416modulates the data and sends the resulting signal through the antennasub-system 124; (3) a processor sub-system 414 that carries outfunctions such as configuring the receiver 418 and transmitter 416sub-systems, processing the data received from the receiver 418sub-system, determining the data to be transmitted through thetransmitter sub-system 416, as well as controlling the antennasub-system 124; and (4) a memory sub-system 412 that contains programcode, configuration data, and system parameters information that areaccessed by the processor 414.

Aerial platforms such as UAVs 110 cruise in a three-dimensional area.The position of the aerial platform 110 with respect to the terminals onthe ground changes as the UAV 110 moves around in a circular/ellipticalmanner in its cruising orbit and also vertically within the “stationkeeping area” (i.e. the UAV's 110 highest orbit 610 and lowest orbit612). If adjustments are not made to the beams generated by the UAV 110based on movements of the UAV 110, then as the UAV 110 moves vertically,the coverage area on the ground that is illuminated by the UAV's antennasub-system 114 will change.

FIG. 2A is an exemplary diagram of the cruising area of a networkconsisting of two UAVs 110-1 and 110-2. The suffixes 1 and 2 are used tolabel the same attributes of the different UAVs in FIG. 2A. Top solidcircles 610-1 and 610-2 show the cruising orbit of the UAVs 110-1 and110-2 at their highest possible altitude. The lower dotted circles 612-1and 612-2 show the cruising orbits at their lowest cruising altitude.Typically, a UAV 110 will cruise around an orbit at a given altitude butat the same time will be slowly moving vertically up or down dependingon time of day (so as to e.g., reduce power consumption, etc.). Inaddition to the vertical movement, the UAV 110 also rolls or pitches asit travels in its cruising orbit.

Various embodiments of the present invention can have different orbitalpaths 610 of the UAV 110. Path shapes may comprise an elliptical orsubstantially circular orbit. Other paths 610, 612 include starpatterned, clover, flower, FIG. 8, or virtually any possible flightpath. Those skilled in the art would also understand the presentdisclosure contemplates orbital paths that are not just parallel to theground. Orbits 610, 612 may also include ones that are vertical innature or encompass three dimensional flight paths. In one set ofembodiments, orbits 610, 612 may also be random, or random withincertain constraints or spatial boundaries, or include orbits withdistinct angular corners (i.e., triangular, quadrilateral, or othermulti-sided orbit).

One set of embodiments in this disclosure describes systems and methodsto optimize the network of beams formed on the ground by multipleadjacent UAVs 110. Another set of embodiments describe a UAV deploymentscheme whereby multiple UAVs 110 may provide coverage to groundterminals 120 in the same coverage area on the same frequency band.

As illustrated in the embodiment FIG. 2A, two UAVs 110-1 and 110-2 andtheir respective coverage areas 614-1 and 614-2 are divided into cells.The desired target coverage area on the ground is divided into a numberof cells, shown as hexagonal cells ranging from 1-19 and 20-38. The UAV110 forms beams to cover each cell on the ground in its target coveragearea 614. FIG. 2A shows an example where UAV 110-1 generates a set ofbeams 1 through 19 in the target coverage area 614-1, and UAV 110-2generates a set of beams 20 through 38 in its target coverage area 614-2on the ground. As illustrated, the hexagons show the ideal coverage ofeach beam. In reality, the beams overlap as shown by the circles overeach hexagonal cell. Frequency reuse (i.e., frequencies allocated to aservice that are reused in a regular pattern of areas or cells) of threeis used in the example of FIG. 2A. In the illustrated embodiment, theavailable frequency bandwidth is divided into three bands and the threefrequency bands are assigned to adjacent beams in such a way that no twoneighboring beams within the coverage area of one UAV 110 use the samefrequency band. The three different dotted circle types (dotted,dot-dashed, dashed) indicate beams that use different frequency bands. Afrequency reuse of three reduces interference at adjacent beams andimproves the data rate. The beams formed by the UAV antenna sub-system114 are typically designed to have a roll-off of 2 to 3 dB at the celledge relative to the beam's peak gain at the center of the cell. Otherembodiments may be designed to incorporate beams formed with a roll-offof greater or less than 2 to 3 dB from the beam's peak gain. The beams,therefore, cover a larger area than that shown by hexagonal shape cellbut at lower gains.

In one embodiment of this disclosure, the UAV 110 and the groundterminal antenna sub-systems 124 are comprised of two antennapolarization such as vertical and horizontal linear polarizations, orleft and right circular polarizations. The UAV 110 and ground terminalradio sub-systems 124 also comprise of two transmitter and two receiverchains, each of the transmitters and receivers connected to one of thetwo antenna polarizations. The UAV 110 and ground terminal radiosub-systems 124 are capable of transmitting and receiving two datastreams, one on each of the two antenna polarizations, resulting in a socalled 2×2 Multiple Input Multiple Output (MIMO) configuration. Eachpair of transmit/receive sub-system of the radio sub-system is referredto as a transceiver in the sequel. The resulting 2×2 MIMO configurationas described above may result in almost doubling the system throughput,using the same amount of spectrum.

In another embodiment of this disclosure, a modified version of IEEE802.11 air interface protocol, also known generically as Wireless LocalArea Network (WLAN) and/or the trademarked name “Wi-Fi”, is used by theUAV 110 and ground terminal radio sub-systems 124 as the communicationsprotocol. The UAV 110, as described above, forms a number of beams tocover the target coverage area 614 on the ground. Each of the beamsformed by the UAV 110 uses a different transceiver to send and receivedata from ground terminals 120 in that beam. The IEEE 802.11specification uses Carrier Sense Multiple Access/Collision Avoidance(CSMA/CA) protocol as a way to prevent user terminals from interferingwith one another when they transmit data over the wireless medium.Embodiments of the present disclosure may use the CSMA/CA framework asdescribed in e.g., IEEE 802.11.

Although CSMA/CA is an effective protocol for handling data transfercollisions over Wi-Fi for LAN where all user terminals are relativelyclose to the base station, CSMA/CA may be ineffective for handlingtransmissions in a point-to-multipoint system over long distances suchas between UAVs 110 and the ground terminals 120. Using CSMA/CA overlong distances in a point-to-multipoint system between the UAV 110 andthe ground terminals 120 may be ineffective because ground terminals 120that are closer to the UAV 110 will dominate the channel arbitrationprocess since they will always be able to sense the channel availabilityfaster than more remote terminals and thus be able to transmit beforeremote terminals do. This effect is sometimes also referred to as the“near-far” problem. In addition to the near-far problem in CSMA/CAschemes, in Time Division Duplex (TDD) modes (which is specified for usewith IEEE 802.11), the two communications links communicate on the samefrequency channel but at different times; thus, when radios are deployedin close proximity to one another, radio interference becomes an issue.If the different transmitters are not synchronized and the transceiversare a short distance apart, the received signal from one transmitter maybe very strong and could severely degrade the performance for all of theradio receivers at the same location even if adjacent transceivers maybe operating in different non-overlapping frequencies and have antennaspointed in different directions. Inside the UAV platform 110, the groundterminal 120 and the gateway transceivers 130 can be placed in closeproximity.

In order to solve the CSMA/CA related issues, the radio sub-systems atthe ground terminals 120, the gateways 130 and the UAV 110 may run acustom Medium Access Control (MAC) layer on top of the IEEE 802.11 PHY.In one exemplary embodiment, the MAC layer will handle the challenges oftransmitting and receiving data frames over the wireless medium. Inorder to avoid having one set of transmitters at the UAV 110 frominterfering with another set of receivers, all transceivers at the UAV110 must be synchronized so that they transmit almost at the same timeand then go into receive mode almost at the same time. In one embodimentto synchronizing the transceivers, a timing signal from a GPS receiver319 at the UAV 110 is used to provide a common clock to all transceiversand thereby synchronizing the transceivers within the UAV 110. Inanother embodiment for synchronizing the transceivers, one of thetransceivers at the UAV 110 acts as the master and sends its clocktiming to the remaining transceivers to which they synchronize theirclocks. The clock timing may be sent from the master transceiver toother transceivers physically through wires to other transceivers withinthe UAV 110; or the master transceiver may send a beacon message thatcarries the master transceiver's clock timing and the remainingtransceivers within the UAV 110 synchronize their clocks to the timingsignal in the beacon message.

Once the timing of all transceivers at the UAV 110 corresponding todifferent UAV beams are synchronized, then a mechanism is needed tosolve the near far problem described above. In one embodiment, time isdivided into intervals and each time interval is further divided intodownlink and uplink sub-intervals. Each sub-interval is further dividedinto time slots. The first sub-interval in each interval is dedicated todownlink transmissions and is referred to as the downlink sub-interval,where the transceiver at the UAV 110 corresponding to each beamtransmits data to the different terminals within their beams. In anotherembodiment for sending data to ground terminals 120, the transceiver atthe UAV 110 communicating with ground terminals in a given beamtransmits data to different ground terminals 120 in a round robin mannerduring the downlink sub-interval. In one embodiment to the UAV 110allocates time to different ground terminals 120 on the uplink, theground terminals 120 send their uplink bandwidth requirement to the UAVtransceiver during one uplink sub-interval. Then, during the downlinksub-interval following the aforementioned uplink sub-interval, the UAVtransmitter corresponding to a beam allocates time on the uplink to eachterminal for the next uplink sub-interval. In other words, in one uplinksub-interval the ground terminals 120 send data to the UAV transceiverof their beams based on the time allocated to each terminal 120 in theprevious downlink sub-interval, and also send to the UAV transceivertheir uplink bandwidth requirement for the next uplink sub-interval. Ineach uplink sub-interval, certain time slots are allocated to the groundterminals 120 where they send their uplink bandwidth requirement.

To increase the throughput provided in the coverage footprint of a UAV110, one may increase the amount of frequency spectrum used in eachbeam, or increase the number of beams used to cover the given footprint. For instance, the coverage area 614-1 as shown in FIG. 2Aconsists of three rings—the first ring having cell 1, the second ringadding cells 2 through 7 around the first ring (cell 1), and the thirdring adding cells 8 through 19 around the second ring—adding one morering of cells and beams to the beam network of UAV 110-1 will add anadditional 18 beams in the fourth ring around the third ring, resultingin a total of 37 beams in coverage area 614-1. A fifth ring of beamswould add an additional 24 beams, resulting in a total of 61 beams inthe circular footprint. Therefore, the number of rings of cells andbeams used to cover the desired footprint of a UAV 110 depends on therequired throughput and may be adjusted as desired or needed toeffectuate appropriate coverage, consistent with the present disclosure.

Referring back to FIG. 2A, in a UAV static beam forming mechanism (e.g.,where the UAV antenna sub-system 114 does not keep each beam pointed ata given location by either mechanical or electronic beam steering as theUAV 110 cruises in its orbit 614), the beams formed by the UAV 110 onthe ground will move around within a circle (or other orbit) as the UAV110 cruises. In this case, the beams shown within circles 614-1 and614-2 will rotate around the center of the coverage areas as therespective UAV 110 travels in its orbit. As a beam moves over a groundterminal 120 and the neighboring beam provides better coverage to theterminal, the ground terminal will be switched to the beam with bettercoverage. The advantage of this type of static UAV beam forming is thatit reduces UAV antenna sub-system 114 complexity.

In one embodiment of static UAV beam forming, the beams formed bydifferent UAVs 110 may rotate on the ground at different rates becauseof different movements of the UAVs 110. In other words, with static UAVbeam forming, certain beams at the boundary between two different UAVs110 may end up using the same frequency band. In that case, thethroughput at the boundary beams which use the same frequency band maybe lower than that of the beams further inside each coverage area. Oneapproach to improving the data rates at the boundary beams that use thesame frequencies would be to use the same frequency band in a TimeDivision Multiplex (TDM) manner between boundary beams of two UAVs 110.For instance, terminals that are at the boundaries of beam 12 of UAV110-1 and beam 37 of UAV 110-2 may use the same frequency but atdifferent times, where at a given time only one of the UAVs 110 istransmitting to terminals 120 in its coverage area.

In another embodiment, the available frequency spectrum in the samefrequency boundary cells is divided into two frequency sub-bands, andeach sub-band is assigned to one of the neighboring boundary beams. Inother words, in the beams within each coverage area, a first frequencyreuse factor could be used (e.g., three (3)), but for cells at certainboundaries, the effective frequency reuse would be doubled (e.g., six(6)). In this manner, the beams at those boundaries can share theavailable frequency spectrum.

Dividing the spectrum between certain adjacent boundary beams, reducesthe throughput in those beams proportionately compared to beams insidethe coverage area. Accordingly, in some variants, the UAV radiosub-system 112 allocates more transmit power to the beams with thereduced spectrum as that of other beams to compensate for the loweredthroughput due to the division of the available frequency band. Theadditional transmit power increases the throughput per unit of spectrumbandwidth in the beams with less spectrum. The throughput of beams withlarger coverage areas or higher traffic intensity may also be increasedby increasing the transmit power in the corresponding beams. In thismanner, beam transmit power control is needed to adjust the throughputof the different beams based on the beams' coverage area, trafficrequirements, and the amount of spectrum allocation. Moreover, beamtransmit power control may also be used to adjust the beam's power inresponse to rain fade. Therefore, the power amplifier (PA) 317 allocatedto a beam will be adjusted over a certain dynamic range based on theabovementioned conditions. The processor sub-system 314 has knowledge ofeach beam's traffic requirement, allocated frequency, coverage area,and/or atmospheric conditions. Based on the aforementioned information,the processor 314 determines the required power to be allocated to eachbeam, and instructs the radio sub-system 112 to adjust the power of thePA sub-system 317 for each beam accordingly.

In some embodiments, the dynamic range of the PA 317 is large and the PAoutput versus input power may have linearity requirements. In suchimplementations, the power consumption of the PA 317 may be large as thePA 317 must be biased to cover the large dynamic range. In this case,the PA bias will be large resulting in high PA power consumption evenwhen the actual PA transmit power is low. Since a UAVs' 110 availablepower may be limited, a mechanism for minimizing the power consumptionof the PA 317 while allowing PA transmit power control over a widedynamic range may be required. In one exemplary embodiment, the requireddynamic range of the power control is divided into N power sub-ranges tominimize the PA power consumption. The PA 317 is designed to includemultiple bias points, where each PA bias point corresponds to one of theN power sub-ranges. Then, when the PA 317 is operating in the j-th powersub-range, the j-th PA bias point corresponding to the j-th powersub-range will be used by the PA 317. In other words, the PA bias isoptimized for the specific power sub-range at which the PA 317 isinstructed by the power control algorithm to operate. When PA transmitpower is at a lower sub-range, the PA bias is also set lower, resultingin a lower PA power consumption than a PA 317 with single but largerbias.

FIG. 2B illustrates an alternate configuration in which three sets ofbeams are formed by three adjacent UAVs 110. Under the assumptions thatthree UAVs 110 may cruise at different speeds, and that UAV antennastatic beam forming is employed, then beams at the boundary of coverageareas 614-1, 614-2 and 614-3 may at certain time use the same frequencyband as discussed above. As mentioned above, UAV beams are typicallydesigned to roll off by 2 to 3 dB at the cell edge on the ground.Consequently, the UAV beam still provides coverage but at lower gainbeyond the cell's edge. More directly, beams formed by the UAV 110 canprovide coverage to a larger area than specified by the hexagonboundaries in FIG. 2B, but with lower gain. As can be seen, there are nodedicated beams directly covering the area 615 near where the threecoverage areas 614-1, 614-2 and 614-3 intersect. However, as shown, area615 is adjacent to areas which are covered by beams 27 and 54. Asdiscussed above, some of the boundary beams, such as beams 27 and 54which use the same frequency band as indicated by the dotted circlesover beams 27 and 54, may divide the available frequency between the twobeams to reduce co-channel interference and to improve data rate. Sincethe boundary beams 54 and 27 “bleed” into a larger area and effectivelyhave access to half of the spectrum versus other beams, then asdiscussed above, the UAVs may increase the power allocated to thesebeams to improve their throughput and compensate for their smallerfrequency spectrum and larger coverage.

Another embodiment of this disclosure describes systems and methods tomanage sets of beams between multiple neighboring UAVs 110 when the UAVantenna sub-system 114 has the capability to dynamically steer its beamsin response to UAV 110 movements where the beams stay fixed onpredetermined ground positions. The dynamic beam forming may beimplemented using either mechanical or electronic beam steeringmechanisms. The UAV antenna sub-system 114 periodically receives UAVposition location coordinates as well as UAV orientation angles fromaccelerometer/gyroscope/GPS sub-system 319 of the UAV 110. The UAVantenna sub-system 114 then uses the updated UAV position coordinatesand orientation angles to steer the beams to remain fixed in theirassigned positions on the ground. Thus, the beams stay fixed to theirassigned positions even when the UAV 110 moves.

With dynamic UAV beam steering, the beams covering the different cellsremain fixed on those cells and do not substantially move overtime. Inthis case, it is possible to design a frequency reuse scheme among thecells 1-75 on the ground so that even boundary cells and beamscorresponding to different UAVs 110 use different frequencies. FIG. 2Cillustrates one embodiment in which the cells within coverage area 616among multiple UAVs 110 are efficiently divided. This is followed bysuperimposing a frequency reuse, such as reuse of three, on the cellscovering the area to be served by multiple UAVs 110. Next, the cells1-75 are divided between coverage areas of different UAVs 110. FIG. 2Cillustrates how part of the ground coverage area is divided into twoareas of 614-1 and 614-2, each covered by a different UAV 110. In thisexample, the coverage area provided by each UAV 110 is approximated by asquare. One possible principle in dividing cells between UAVs 110corresponding to the two areas 614-1 and 614-2 is to assign a cell to aUAV 110 if at least 50% of the cell's area is covered by thecorresponding UAV 110. For instance, cells 46, 47 and 48 would not beassigned to coverage area 614-1 because 614-1 covers less than 50% ofthe aforementioned cells. But cells 41 and 42 are assigned to coveragearea 614-1 and are severed by the UAV 110 that provides coverage to614-1. Cases in which 50% of a cell's area is covered may be resolvedthrough arbitrary, predetermined, or alternating assignment (ortime-averaged if not always fixed, as discussed immediately below).Various schemes for dividing coverage areas for different UAVs 110 canbe used. The remainder of area 616 may be similarly assigned to otherUAVs 110.

In further embodiments other coverage criteria are used to determinecell assignment. For example, in some embodiments a cell will not beassigned to a UAV 110 unless it can cover a supermajority of area (e.g.75%) up to 100%. In other embodiments, a UAV 110 may be assigned a cellwith less coverage (i.e. below 50%). Furthermore, embodiments may alsouse other criteria rather than just coverage area to determine whether acell should be assigned to a particular UAV 110 such as the particularsof the UAVs 110 and their configurations, and/or network considerations(e.g., current usage, historic usage, predicted usage, etc.)

In other embodiments, depending on the periodicity of updates of the UAVposition and orientation from the accelerometer/gyroscope/GPS sub-system319 of the UAV 110, the beam positions can stay fixed as described inabove embodiments or allowed to move away from their original positionsfor a length of time. If the UAV coordinates are updated slowly, thebeam positions would also be adjusted accordingly. Depending on theconnectivity demand associated with the particular ground positions,this configuration may reduce operating costs, e.g., battery life on theUAV 110. Infrastructures or areas with sensitive resource considerationsmay thereby opt to increase the update periods to reduce upkeep costs.

Referring now to FIGS. 3A and 3B, a UAV deployment strategy is describedwhereby multiple UAVs 110 may provide coverage to their respectiveground terminals in the same coverage area and on the same frequencyband. In an exemplary embodiment of the deployment scheme, two differentoperators would be allowed to provide broadband service to theirrespective customers in the same geographic area using the samespectrum. FIG. 3A shows two UAVs 110-1 and 110-2 cruising in orbits610-1 and 610-2. The coverage areas 614-1 and 614-2 of the two UAVs110-1 and 110-2 overlap as shown by the two circles with different typesof dashed lines. Separation between UAVs 110-1 and 110-2 is achieved byspacing the cruising orbit of the two UAVs 110-1 and 110-2 and alsoplacing the UAVs 110-1 and 110-2 in their respective cruising orbits610-1 and 610-2 to further increase the separation between the UAVs110-1 and 110-2.

In contrast to having separate cruising orbits 610-1 and 610-2, UAVs mayoverlap in their cruising orbits, as depicted in FIG. 3B. Both UAVs110-1 and 110-2 share a same cruising orbit 610, but the two UAVs 110-1and 110-2 cruise in such a way so as to maintain a certain separationdistance between the two UAVs 110-1 and 110-2. Each UAV 110-1 and 110-2provides connectivity to a different set of ground terminals 120. FIGS.3A and 3B show ground terminal 120-1 communicating with UAV 110-1, andground terminal 120-2 communicating with UAV 110-2. If both UAVs 110-1and 110-2 use the same frequency band in the same coverage area 614,then ground terminals 120 communicating with a first UAV 110-1 mustdeploy directional antennas pointed toward the first UAV 110-1 in orderto attenuate the interference received from signals transmitted by thesecond UAV 110-2. Ground terminal 120-1 points its beam toward UAV110-1. If there is a spatial separation between the two UAVs 110-1 and110-2, and the antenna beam of the ground terminal 120-1 is chosen to beadequately narrow, then the sidelobe of the ground terminal 120-1antenna beam will attenuate the signal received from UAV 110-2. Therequired ground terminal 110-1 antenna sidelobe attenuation toward UAV110-2 depends on the desired Signal to Interference ratio (S/I) atground terminal 120-1. The larger the desired S/I, the larger therequired attenuation of ground terminal beam sidelobe toward theinterfering UAV 110, which in turn requires a narrower beamwidth for theground terminal antenna beam. The required beamwidth of the groundterminal antenna beam also depends on the spatial separation of the twoUAVs 110-1 and 110-2. The closer the two UAVs 110-1 and 110-2 are, thenarrower the beamwidth of the ground terminal must be in order tomaintain the interference from the interfering UAV 110 below athreshold. Therefore, once the required S/I received at the groundterminal and the minimum separation of the two UAVs 110-1 and 110-2 arespecified, then the required beamwidth of the ground terminal beam maybe computed for each ground terminal location in the specified coveragearea 614. The beamwidth of the ground terminal antenna beam is chosen tobe the minimum beamwidth from among all ground terminal locations. Inother embodiments, more than two UAVs 110-1 and 110-2 may share the samecruising orbit 610.

Therefore, by adequately separating the distance between the UAVs 110-1and 110-2 in the cruising orbits 610, by choosing adequately narrowbeamwidth ground terminal antenna beam patterns, and by pointing thebeam of each ground terminal antenna toward the UAV 110-1 or 110-2 withwhich it communicates, it is possible for multiple UAVs 110-1 and 110-2to provide service to ground terminals 120 in the same coverage area anduse the same frequency spectrum. This UAV deployment scheme allows reuseof the same spectrum by multiple UAVs 110 in the same geographical area,thereby making efficient use of the available spectrum. Note that thedifferent UAVs 110 serving the same geographic coverage area may belongto different service providers. The different service providers need toagree on the target S/I, and then compute the required UAV separationand ground terminal antenna beamwidth/pattern to achieve the target S/I.The required UAV separation and ground terminal antenna pattern would bespecified as rules to be followed by the different UAV service providersto achieve the target S/I performance requirement.

In another configuration, cruising orbits 610-1 and 610-2 of UAVs 110-1and 110-2 may overlap partially, as long as the UAVs are positioned soas to not cross paths at an intersection of cruising orbits 610-1 and610-2. The beamwidth for the ground terminal antenna beams may not berequired to be as narrow as in the configuration of FIG. 3B because theUAVs 110-1 and 110-2 may be adequately separated. This is particularlytrue if UAVs 110-1 and 110-2 orbit in a manner that maintains asubstantially fixed distance between them (e.g., UAVs 110-1 and 110-2orbit in the same direction and in parallel). In constant distancevariants, the beamwidth of the ground terminal beam will stay relativelyconstant reducing interference from/to other UAVs 110-1 and 110-2. Onthe other hand, if the distances between UAVs 110-1 and 110-2continually varies (e.g., UAVs 110-1 and 110-2 are orbiting at differentspeeds, and at different angles), then there will be a dynamicallychanging range of distances between the UAVs 110-1 and 110-2. The UAVs110-1 and 110-2 must compensate by adjusting their beamwidths based onthe varying distances created by uneven orbit paths. Where technologicallimits or other signal interferences make it difficult to constantlyemit beams having narrow beamwidths, or where airspace is restricted toa smaller area than would be needed to completely separate cruisingorbits 610-1 and 610-2, a partial overlap of the orbits may provide acompromise.

In some embodiments, when the GTs use adequately narrow beamwidthantennas and the different UAVs, as shown in FIG. 2B, are adequatelyseparated as described in preceding paragraphs, then the groundterminals communicating boundary coverage area cell of one UAV, e.g.,cell 11 of UAV 110-1, can receive negligible interference from theneighboring UAVs 110-2 and 110-3 even if the neighboring cells 27 and 54are using the same frequency as that of cell 11. Consequently, cells atthe boundary of coverage areas of multiple UAVs may use the samefrequency band with negligible interference to the GTs in those cellsand without needing to further divide time or frequency among theboundary cells.

Furthermore, it is contemplated in further embodiments that UAVs 110 maybe able to communicate with other UAVs 110 (or sense the presence orposition of other UAVs 110) to determine an appropriate distance,velocity, and PA output. It is contemplated that UAVs 110 can changeposition and/or orbit depending on the position or movements of otherUAVs 110. For instance, if one of the UAVs 110 were to go offline, otherUAVs 110 can compensate. Additionally, management of a UAV 110 couldoccur from a terminal on the ground and may be manual or automatic. Itwill be recognized that while certain aspects of the disclosure aredescribed in terms of a specific sequence of steps of a method, thesedescriptions are only illustrative of the broader methods of thedisclosure, and may be modified as required by the particularapplication. Certain steps may be rendered unnecessary or optional undercertain circumstances. Additionally, certain steps or functionality maybe added to the disclosed embodiments, or the order of performance oftwo or more steps permuted. All such variations are considered to beencompassed within the disclosure and claims herein.

It will be further appreciated that while certain steps and aspects ofthe various methods and apparatus described herein may be performed by ahuman being, the disclosed aspects and individual methods and apparatusare generally computerized/computer-implemented. Computerized apparatusand methods are necessary to fully implement these aspects for anynumber of reasons including, without limitation, commercial viability,practicality, and even feasibility (i.e., certain steps/processes simplycannot be performed by a human being in any viable fashion).

While the above detailed description has shown, described, and pointedout novel features of the disclosure as applied to various embodiments,it will be understood that various omissions, substitutions, and changesin the form and details of the device or process illustrated may be madeby those skilled in the art without departing from the disclosure. Theforegoing description is of the best mode presently contemplated ofcarrying out the disclosure. This description is in no way meant to belimiting, but rather should be taken as illustrative of the generalprinciples of the disclosure. The scope of the disclosure should bedetermined with reference to the claims.

What is claimed is: 1.-19. (canceled)
 20. A method of relaying Internettraffic via an unmanned aerial vehicle (UAV), the method comprising:associating each of a plurality of ground terminals to respective onesof a plurality of cells; receiving data at the UAV from a gatewayapparatus, the gateway apparatus being in data communication with anInternet; and transmitting a beam comprising at least a portion of thereceived data to the plurality of cells, the associated ones of theplurality of ground terminals being in data communication with the UAV;where adjacent ones of the plurality of cells receive the beam atdifferent frequencies.
 21. The method of claim 20, where the UAV and atleast one ground terminal of the plurality of ground terminals compriseantenna sub-systems that are comprised of two antenna polarizations. 22.The method of claim 21, where the two antenna polarizations comprisevertical and horizontal linear polarizations.
 23. The method of claim21, where the two antenna polarizations comprise left and right circularpolarizations.
 24. The method of claim 21, where both the UAV and the atleast one ground terminal comprise two transmitter and two receiverchains, and where each of the transmitter and receiver chains areconnected to one of the two antenna polarizations.
 25. The method ofclaim 24, where the UAV and the at least one ground terminal areconfigured to transmit and receive two data streams, one on each one ofthe two antenna polarizations.
 26. The method of claim 20, where the UAVforms a plurality of beams to cover a target coverage area on theground.
 27. The method of claim 26, where at least a first one and asecond one of the plurality of beams use different transceivers.
 28. Themethod of claim 20, where the UAV and the ground terminal communicateaccording to an IEEE 802.11 physical air interface protocol.
 29. Themethod of claim 28, where the UAV and the ground terminal are configuredto execute an IEEE 802.11 medium access control (MAC) layer that isconfigured to synchronize to a timing signal generated from a GlobalPositioning System (GPS) receiver
 30. The method of claim 28, where theUAV and the at least one ground terminal are configured to execute anIEEE 802.11 medium access control (MAC) layer that is configured tosynchronize to a master UAV transceiver.
 31. The method of claim 30,where the master UAV transceiver provides a clock timing reference to atleast one other transceiver within the UAV.
 32. The method of claim 30,where the master UAV transceiver provides a clock timing reference via abeacon message to the UAV.
 33. A system for relaying Internet trafficvia an unmanned aerial vehicle (UAV), the system comprising: a networkof one or more unmanned aerial vehicles (UAV) that are configured toassociate to respective ones of a plurality of ground terminals within aplurality of cells; wherein each one of the one or more UAVs areconfigured to receive data from a gateway apparatus, and where thegateway apparatus is in data communication with an Internet; and whereeach one of the one or more UAVs transmit at least a portion of thereceived data to the respective ones of the plurality of groundterminals within the plurality of cells.
 34. The system of claim 33,wherein the network of one or more UAV are synchronized to a commonclock reference.
 35. The system of claim 34, wherein the common clockreference is derived from a beacon message transmitted by a master UAV.36. The system of claim 34, wherein each one of the one or more UAVs areallocated at least one uplink sub-interval and at least one downlinksub-interval that are generated from the common clock reference.
 37. Thesystem of claim 36, wherein each one of the one or more UAVs allocate aplurality of time slots associated with the at least one uplinksub-interval and at least one downlink sub-interval to the respectiveones of the plurality of ground terminals.
 38. A system for relayingInternet traffic via an unmanned aerial vehicle (UAV), the systemcomprising: a gateway apparatus in data communication with an Internet;a network of one or more unmanned aerial vehicles (UAV) that areconfigured to communicate to respective ones of a plurality of groundterminals within a plurality of cells in data communication with thegateway apparatus; and wherein the network of one or more UAVs areassociated with the plurality of cells, and where adjacent ones of theplurality of cells are allocated different frequencies forcommunication.
 39. The system of claim 38, wherein the network of one ormore UAV are synchronized to a common clock reference.
 40. The system ofclaim 39, wherein the network of one or more UAV are configured totransmit or receive during a common time interval based on the commonclock reference.